Large capacity, long-boom cranes are often required for building or assembling structures. Some cranes such as tower cranes are typically assembled on site and disassembled after work is completed. However, for many applications a more mobile, easily deployable crane is more suitable.
Where mobile telescoping cranes are larger and/or their duty loads increase, stability challenges arise. For example, as counterweight is added to a crane, rearward stability problems can manifest, particularly when the crane is on sloping ground. Some large telescoping cranes perform similarly to traditional tower cranes. When fully extended, telescoping members are oriented almost completely vertically, with a crane base, jib, masts, and boom disposed at the end of the telescoping members. As such a crane extends to greater heights, it is increasingly vulnerable to stress from loads and winds, to the detriment of the crane's stability and structural integrity.
One attempt to address this issue is with the Grove® GTK1100 mobile crane, manufactured by Manitowoc Companies, Inc. Among disadvantages of the GTK1100 solution is its requirement for multiple elevated outriggers disposed under the boom of the crane. Each of the elevated outriggers is coupled to the ground via multiple hinged or articulated supports anchored near ground-level outriggers. The elevated outrigger solution results in much additional hardware and weight, as well as a relatively large ground footprint, which can interfere with crane operations.
The elevated outriggers typically project laterally from a crane support structure at least 40 feet above the ground. The elevated outriggers are typically substantially horizontally disposed, and can project from a crane support structure at heights of preferably at least 80 feet above ground, more preferably at least 155 feet above ground, still more preferably at least 230 feet above ground, and most preferably at least 280 feet above ground. Each elevated outrigger typically has its own connection anchoring the elevated outrigger to the ground. Elevated outriggers typically do not attach to a tower structure for stability or support.
Accordingly, a need exists for a heavy-duty crane having greater stability and greater mobility. Decreased footprint and reduced size and weight are also desired.